Field of the Invention
The present invention relates to apparatus and a method for use in printing, specifically for use in the area of printing as implemented in the computing field. More specifically, the present invention relates to apparatus and a method for increasing and decreasing the speed of a print cartridge carrier, in conjunction with the control of the print quality, along an acceleration ramp area having a more optimum design of shorter length. The present invention is particularly beneficial for use within an ink jet printer, but may be incorporated with effect in other serial print systems as well.
Background Developments
Conventional ink jet printers employ a carrier to displace ink-containing print cartridges bi-directionally across a carrier displacement field. The carrier displacement field includes a print line portion (or simply "print line") through which the print cartridges travel to disperse ink, in a controlled manner, onto paper or other suitable media. The carrier displacement field also includes a non-print portion separate from and adjacent to the print line portion. The non-print portion typically comprises two equal-length subportions of the carrier displacement field with each of the two subportions being located adjacent to but on opposite sides of the print line portion of the carrier displacement field.
The non-print subportions of the displacement field are used to uniformly provide on both sides of the print line space for the carrier to acquire (at the start of its travel) and uniformly to lose (at the end of its travel) sufficient speed in accordance with a desired level of print quality as the print cartridge is moved back and forth across the media. In view of this purpose of the non-media subportions of the carrier field, that portion of the displacement field is referred to as the "acceleration ramp area." As one of ordinary skill in the art also would know, the carrier displacement field, at least for ink jet printers, typically also includes another portion, a maintenance station area, that typically is located at the outward-most end of the carrier displacement field and adjacent the outward-most side of one of the two subportions comprising the acceleration ramp area. A maintenance station located in the maintenance station area is used to clean and prepare the cartridge for dispersing ink.
In certain conventional printing systems, the two acceleration ramp area subportions are sized uniformly and with relatively great length to allow the carrier to accelerate to obtain full print speed before reaching the print line on both sides of the print line for all of the carrier's travel through the print line, and to support such carrier travel for the print mode with the highest characteristic speed. Specifically, sufficient acceleration ramp area for the carrier to achieve full operating speed for all of its travel through the print line is provided for printer function in the lower quality mode known as "draft mode."
In draft mode, the print cartridge disperses approximately half as much ink as it would be required to do in higher quality print modes such as "letter mode." Because the print cartridge is dispersing half as much ink in draft mode, it is useful to move the carrier through the print line at about twice the speed desired in letter mode. Without changing other operational characteristics such as acceleration rate (which change requires, among other things, use of a relatively larger power supply), obtaining that higher draft mode speed requires a relatively long acceleration ramp area of the kind conventionally provided. Unfortunately, however, longer ramps undesirably increase the size, cost and print quality of printing systems.
Other known printing systems take a different approach to acceleration ramp area sizing. Such systems address the cost/size versus print quality dilemma that is described above by uniformly reducing by a predetermined amount the length of the uniformly-sized non-print subportions of the acceleration ramp area. More specifically, the length of both acceleration ramp area subportions is modestly and uniformly reduced so the carrier reaches less than full draft mode print speed (i.e., less than, for example, 33 inches per second ("i.p.s.")) at the time the carrier reaches the print line and draft mode printing begins. The reduction in acceleration ramp area is an acknowledgment of the fact that ramp sizing in the earlier-described systems was done to prevent any degradation in print quality for a mode, which has as its very purpose allowing printing at lower quality. In view of the purpose of draft mode, ramp area sizing need not be controlled by the full draft mode speed.
In conventional systems, which have the size of both subportions of the acceleration ramp area uniformly reduced, both subportions support attaining something less than full speed for draft mode upon entering the print line, but fully support, at the start of and throughout the entire print line, attaining the slower speed required for high quality letter mode printing.
Illustratively, letter mode printing can be achieved with the carrier traveling at 15 i.p.s. through the print line, having been accelerated at 384 inches/s.sup.2 (or "1.0 g") through the ramp area. An acceleration ramp area subportion of sufficient length to allow a carrier accelerating at 1.0 g to enter the print line at 15 i.p.s. may have, for example, a length of approximately 0.30 inches. On the other hand, the ramp area to support entry of the carrier into the print line at a full draft mode speed of, for example, 33 i.p.s. and accelerating at 1.0 g from rest would be approximately 1.42 inches long, which is a significantly greater length. However, using the shorter length required to support full letter mode speed still would permit the carrier, operating in draft mode, to achieve a speed significantly in excess of approximately 8.25 i.p.s. or 25% of the full draft mode speed of 33 i.p.s. upon print line entry. And any percentage of full speed in this 25% or greater range has been viewed as an acceptable speed for commencing draft mode printing.
Since conventional printing systems with uniformly shortened acceleration ramp area subportions begin draft mode printing at less than full speed, such systems typically also incorporate improved mechanisms or subsystems that enable adjustment of the dispersion of the ink from the print cartridge in accordance with actual cartridge speed (as opposed to the desired, but-not-yet-realized speed) of the accelerating print cartridge. Such apparatus and methods simply may involve the use of improved servo devices to more effectively regulate machine function during acceleration of the carrier on both ends of the displacement field.
While the above-described approach to acceleration ramp area sizing makes possible an advantageous reduction in the size and, thus, in the cost of printing systems without too great a loss in print quality, it should be recognized that the foregoing conventional shortened-ramp approach rigidly treats both ramp area subportions uniformly, without consideration of any differences in function of the two subportions. Specifically, the conventional approach ignores differences in how the two subportions typically are used to implement draft mode printing and letter mode (or other high quality mode) printing. Accordingly, any further size reductions that would have been made possible by considering such differences have not heretofore been considered or implemented.
The present invention relies upon such differences. Specifically, the fact that printing in quality modes, e.g., letter mode involves only un-idirectional acceleration of the carrier and uni-directional printing in the print line, while draft mode acceleration and printing operates bi-directionally, has been relied upon to reduce the total acceleration ramp area for a printing system even further, and, by so doing, further reduce overall system size and cost.